JP5106180B2 - Toner for electrophotography - Google Patents

Description

  The present invention relates to an electrophotographic toner used for developing a latent image formed in an electrophotographic method, an electrostatic recording method, an electrostatic printing method or the like.

Properties required for the toner include low-temperature fixability and hot offset resistance. Therefore, as an attempt to achieve both low-temperature fixability and hot offset resistance, many toners that use a polyester resin having a low softening point and a polyester resin having a high softening point have been studied (see Patent Documents 1 to 3, etc.).
JP 2003-119351 A JP-A-60-214368 JP 2000-347451 A

  These techniques realize improvement in low-temperature fixability by using a polyester having a low softening point and improvement in hot offset resistance by using a polyester having a high softening point, and are intended for functional separation. Therefore, it is desirable that the difference between the softening points of the two polyesters is somewhat large, but in general, a polyester with a large difference in softening points has a large viscosity difference. When both polyesters are used together, the two polyesters are uniformly distributed during melt-kneading. In addition, if the high softening point portion and the softening point portion are in a non-uniform state, both the low-temperature fixability and the hot offset resistance are reduced, and the peelability from the fixing roller and the toner pulverization property are also deteriorated. . Therefore, by using polyester with a small softening point difference, two polyesters can be mixed uniformly, but functional separation is not possible, and the softening point of the low softening point polyester is increased, or the softening point of the high softening point resin is softened. Since the point becomes lower, either the low-temperature fixability or the hot offset resistance deteriorates.

  An object of the present invention is to provide an electrophotographic toner that is excellent in all of low-temperature fixability, hot offset resistance, releasability from a fixing roller, and toner pulverization property even if it contains a polyester having a large softening point difference. There is to do.

  The present invention relates to an electrophotographic toner comprising, as a binder resin, polyester H and polyester L having a softening point 55 to 80 ° C. lower than that of polyester H, wherein the polyester L is an ethylene oxide adduct of bisphenol A. The present invention relates to a toner for electrophotography, which is a polyester obtained by condensation polymerization of an alcohol component containing 30 to 100 mol% and a carboxylic acid component.

  The electrophotographic toner of the present invention exhibits excellent effects in all of low-temperature fixability, hot offset resistance, releasability from a fixing roller, and toner pulverization property even if it contains a polyester having a large softening point difference. Is.

  In the electrophotographic toner of the present invention, the polyester H and the polyester L having a lower softening point than the polyester H contained as a binder resin, the polyester L which is a polyester having a lower softening point is an ethylene oxide adduct of bisphenol A It is characterized in that it is a polyester obtained by polycondensation of an alcohol component and a carboxylic acid component containing a specific amount. Conventionally, in a toner containing two types of polyesters having different softening points, it is necessary to separate the functions in order to achieve both low-temperature fixability and hot offset resistance. Since different resins are mixed together, the softening point portion and softening point portion are present in the binder resin, resulting in a non-uniform state and a decrease in fixability. Therefore, the softening point difference cannot be increased, and the low softening point polyester and The function of the high softening point polyester could not be exhibited effectively. However, in the present invention, since a specific amount of an ethylene oxide adduct of bisphenol A is used as the alcohol component of the low softening point polyester, both low temperature fixability and hot offset resistance are improved. It is possible to prevent a decrease in toner detachability from the fixing roller and toner pulverization property, that is, a decrease in pulverization property of the melted and kneaded material of the toner raw material in the toner production process due to the presence of a softening point portion and an uneven state. it can. This is presumably due to the fact that the number average molecular weight of the obtained polyester can be made higher than that of the polyester having the same softening point by using the ethylene oxide adduct of bisphenol A as the alcohol component. That is, since the propylene oxide adduct has a rigid monomer structure, it requires a relatively small amount of monomer to react until reaching a predetermined softening point, whereas in the case of an ethylene oxide adduct, the monomer structure is soft. Many monomers react before reaching a predetermined softening point. Therefore, even if the polyester has a low softening point, the number average molecular weight is about the same as that of the high softening point resin, and it is estimated that the non-uniform state of the binder resin due to the viscosity difference does not occur.

  The difference in softening point between polyester H and polyester L is 55 to 80 ° C. from the viewpoint of low-temperature fixability and hot offset resistance of the toner, and preferably 57 to 75 ° C. from the viewpoint of dispersibility of the internal additive. Is 58 to 72 ° C, more preferably 59 to 65 ° C.

  The polyester L is obtained by using an alcohol component and a carboxylic acid component as raw material monomers and subjecting them to condensation polymerization.

  Examples of the alcohol component include polyoxypropylene-2,2-bis (4-hydroxyphenyl) propane and polyoxyethylene-2,2-bis (4-hydroxyphenyl) propane, which are represented by the formula (I):

(In the formula, RO and OR are oxyalkylene groups, R is an ethylene and / or propylene group, x and y indicate the number of added moles of alkylene oxide, each being a positive number, and the sum of x and y. 1 to 16 is preferable, 1 to 8 is more preferable, and 1.5 to 4 is more preferable)
Aromatic diols such as alkylene oxide adducts of bisphenol represented by: ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6 -Aliphatic diols such as hexanediol, 1,4-butenediol, 1,3-butanediol and neopentyl glycol, and trihydric or higher polyhydric alcohols such as glycerin. Among these, an alkylene oxide adduct of bisphenol A is preferable from the viewpoint of chargeability of the toner.

  As described above, from the viewpoint of low-temperature fixability, hot offset resistance, releasability from the fixing roller, and grindability, the alcohol component of polyester L is obtained by adding bisphenol A ethylene oxide adduct (BPA-EO) to alcohol. In a component, it contains 30-100 mol%, Preferably it is 50-95 mol%, More preferably, it contains 70-90 mol%. Further, from the viewpoint of releasability of the toner from the fixing roller, the content of the propylene oxide adduct (BPA-PO) of bisphenol A is preferably 0 to 70 mol%, more preferably 5 to 50 mol% in the alcohol component. Preferably, 10 to 20 mol% is more preferable. The molar ratio of BPA-EO to BPA-PO (BPA-EO / BPA-PO) is more preferably 1.0 to 20, more preferably 4.0 to 10, from the viewpoints of toner release from the fixing roller and hot offset resistance. preferable.

  In the present invention, the ethylene oxide adduct of bisphenol A is preferably a compound in which R is an ethylene group in the alkylene oxide adduct of bisphenol A represented by formula (I), but within the range not impairing the effects of the present invention. In addition, a part of the ethylene group may be substituted with another alkylene group containing a propylene group. Similarly, the propylene oxide adduct of bisphenol A is preferably a compound in which R is a propylene group in the alkylene oxide adduct of bisphenol A represented by the formula (I), so long as the effects of the present invention are not impaired. It may be substituted with another alkylene group containing a group.

  Examples of carboxylic acid components include oxalic acid, malonic acid, maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, n-dodecyl succinic acid, n-dodecenyl succinic acid, etc. Aliphatic dicarboxylic acids; aromatic dicarboxylic acids such as phthalic acid, isophthalic acid and terephthalic acid; alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid; trivalent or higher polyvalent carboxylic acids such as trimellitic acid and pyromellitic acid; And anhydrides of these acids, alkyl (1 to 3 carbon atoms) esters; rosins; rosins modified with fumaric acid, maleic acid, acrylic acid, and the like. Such acids, anhydrides of these acids, and alkyl esters of these acids are collectively referred to herein as carboxylic acid compounds. The carboxylic acid component of at least one of polyester H and polyester L preferably contains an aromatic dicarboxylic acid compound in an amount of preferably 50 mol% or more, more preferably 60 mol% or more, and even more preferably 75 mol% or more. desirable.

  The carboxylic acid component of the polyester L is preferably an aliphatic dicarboxylic acid compound, more preferably fumaric acid or maleic acid, from the viewpoint of low-temperature fixability of the toner. The content of the aliphatic dicarboxylic acid compound is preferably 15 to 70 mol%, more preferably 18 to 60 mol%, still more preferably 20 to 40 mol% in the carboxylic acid component from the viewpoint of low-temperature fixability of the toner. . As the carboxylic acid component other than the aliphatic dicarboxylic acid, an aromatic dicarboxylic acid compound is preferable.

  The alcohol component contains a monovalent alcohol, and the carboxylic acid component contains a monovalent carboxylic acid compound as appropriate from the viewpoint of adjusting the molecular weight of the polyester and improving the offset resistance of the toner containing the polyester. May be.

  The polycondensation of the alcohol component and the carboxylic acid component is carried out, for example, in an inert gas atmosphere, further under reduced pressure, in the presence of an esterification catalyst such as tin (II) octylate, dibutyltin oxide, etc. At a temperature of

  The softening point of the polyester L is preferably 75 to 95 ° C, more preferably 80 to 92 ° C, and still more preferably 83 to 90 ° C, from the viewpoint of low-temperature fixability of the toner.

  The glass transition point of the polyester L is preferably from 30 to 70 ° C, more preferably from 35 to 65 ° C, and even more preferably from 40 to 60 ° C, from the viewpoint of toner pulverization.

  The acid value of the polyester L is preferably 5 to 20 mgKOH / g, more preferably 8 to 19 mgKOH / g, and further preferably 10 to 18 mgKOH / g, from the viewpoint of the chargeability of the toner.

  The number average molecular weight of the polyester L is preferably 1000 to 3500, more preferably 1500 to 3000, and further preferably 1600 to 2500 from the viewpoint of hot offset resistance of the toner, peelability from the fixing roller, and grindability.

  Similarly to the polyester L, the polyester H is obtained by condensation polymerization using an alcohol component and a carboxylic acid component as raw material monomers. The same compound is exemplified as the alcohol component and the carboxylic acid component, but as the alcohol component of the polyester H, the content of the bisphenol A ethylene oxide adduct (BPA-EO) is, from the viewpoint of toner pulverization, In an alcohol component, 10-100 mol% is preferable, 20-50 mol% is more preferable, 30-40 mol% is still more preferable. Further, from the viewpoint of pulverizing property of the toner, the content of the propylene oxide adduct (BPA-PO) of bisphenol A is preferably 0 to 90 mol%, more preferably 50 to 80 mol% in the alcohol component, and 60 to 70 mol% is more preferable. The molar ratio of BPA-EO to BPA-PO (BPA-EO / BPA-PO) is preferably from 0.2 to 1.0, more preferably from 0.3 to 0.7, from the viewpoint of toner grindability.

  The carboxylic acid component of polyester H is preferably an aromatic dicarboxylic acid compound from the viewpoint of toner charging properties, and more preferably at least one selected from the group consisting of terephthalic acid, isophthalic acid and phthalic acid. The content of the aromatic dicarboxylic acid compound is preferably 50 to 99 mol%, more preferably 60 to 95 mol%, and more preferably 75 to 90 mol in the carboxylic acid component, from the viewpoints of releasability from the toner fixing roller and grindability. More preferred is mol%. Further, from the viewpoint of hot offset resistance of the toner, a trivalent or higher polyvalent carboxylic acid compound is preferable, and trimellitic acid is more preferable. From the viewpoint of hot offset resistance, the content of the trivalent or higher polyvalent carboxylic acid compound is preferably 1 to 35 mol%, more preferably 3 to 30 mol%, and more preferably 6 to 16 mol% in the carboxylic acid component. Further preferred.

  The softening point of the polyester H is preferably 135 to 160 ° C, more preferably 135 to 155 ° C, and further preferably 135 to 150 ° C, from the viewpoint of low-temperature fixability of the toner.

  The glass transition point of the polyester H is preferably 40 to 80 ° C., more preferably 50 to 75 ° C., and further preferably 55 to 70 ° C. from the viewpoint of toner pulverization.

  The acid value of the polyester H is preferably 1 to 10 mgKOH / g, more preferably 3 to 9 mgKOH / g, and further preferably 4 to 8 mgKOH / g, from the viewpoint of the chargeability of the toner.

  The number average molecular weight of polyester H is preferably from 2000 to 3400, more preferably from 2300 to 3200, and even more preferably from 2600 to 3100, from the viewpoints of toner grindability, hot offset resistance, and releasability from the fixing roller.

  The ratio of the number average molecular weight of the polyester L and the polyester H (H / L) is to reduce the non-uniform state of the binder resin due to the difference in viscosity, and from the viewpoint of increasing the releasability of the toner from the fixing roller and the grindability of the toner 0.8-1.6 are preferable, 0.85-1.6 are more preferable, and 0.9-1.55 are still more preferable.

  The weight ratio (H / L) of polyester L to polyester H is preferably 30/70 to 60/40, more preferably 35/65 to 50/50, and 38/62 to 45 from the viewpoint of low-temperature fixability of the toner. More preferred is / 55.

  The total content of polyester L and polyester H is preferably 60 to 100% by weight in the binder resin from the viewpoints of dispersibility of the internal additive, resistance to hot offset of the toner and releasability from the fixing roller, and 65 to 100 wt% is more preferable, and 75 to 100 wt% is more preferable.

  The toner further includes a colorant, a charge control agent, a release agent, a magnetic powder, a fluidity improver, a conductivity regulator, an extender pigment, a reinforcing filler such as a fibrous substance, an antioxidant, an anti-aging agent, Additives such as a cleaning property improving agent may be appropriately contained.

  As the colorant, all of the dyes and pigments used as toner colorants can be used, such as carbon black, phthalocyanine blue, permanent brown FG, brilliant first scarlet, pigment green B, rhodamine-B base, Solvent Red 49, Solvent Red 146, Solvent Blue 35, Quinacridone, Carmine 6B, Isoindoline, Disazo Yellow and the like can be used, and the toner of the present invention may be either black toner or color toner. The content of the colorant is preferably 1 to 40 parts by weight and more preferably 2 to 10 parts by weight with respect to 100 parts by weight of the binder resin.

  As the charge control agent, any one of negative chargeability and positive chargeability can be used. Examples of the negatively chargeable charge control agent include metal-containing azo dyes, copper phthalocyanine dyes, metal complexes of salicylic acid alkyl derivatives, and nitroimidazole derivatives. Examples of the positively chargeable charge control agent include nigrosine dyes, triphenylmethane dyes, quaternary ammonium salt compounds, polyamine resins, and imidazole derivatives. Also, a polymer type such as a resin can be used. The content of the charge control agent is preferably 0.1 to 8 parts by weight and more preferably 0.2 to 5 parts by weight with respect to 100 parts by weight of the binder resin.

  As release agents, aliphatic hydrocarbon waxes such as polypropylene, polyethylene, polypropylene polyethylene copolymer, microcrystalline wax, paraffin wax, Fischer-Tropsch wax and oxides thereof, carnauba wax, montan wax, sazol wax And ester waxes such as deoxidized wax, fatty acid amides, fatty acids, higher alcohols, fatty acid metal salts and the like, and these may be contained alone or in admixture of two or more. The content of the release agent is preferably 0.1 to 20 parts by weight and more preferably 0.5 to 10 parts by weight with respect to 100 parts by weight of the binder resin.

  The electrophotographic toner of the present invention may be a toner obtained by any conventionally known method such as a melt-kneading method, an emulsion phase inversion method, or a polymerization method. From the viewpoint, a pulverized toner by a melt-kneading method is preferable. In the case of pulverized toner by the melt-kneading method, for example, raw materials such as a binder resin and a colorant are uniformly mixed with a mixer such as a Henschel mixer, and then a sealed kneader, a single or twin screw extruder, an open roll type It can be produced by melt-kneading with a kneader or the like, cooling, pulverizing and classifying. On the other hand, from the viewpoint of reducing the particle size of the toner, a toner by a polymerization method is preferable. An external additive such as hydrophobic silica may be added to the surface of the toner.

The volume median particle size (D ₅₀ ) of the toner is preferably 3 to 15 μm, more preferably 3 to 10 μm. In the present specification, the volume-median particle size (D ₅₀ ) means a particle size at which the cumulative volume frequency calculated by the volume fraction is 50% when calculated from the smaller particle size.

  The toner of the present invention can be used as a one-component developing toner or as a two-component developer mixed with a carrier.

[Softening point of resin]
Using a flow tester (Shimadzu Corporation, CFT-500D), a 1 g sample is heated at a heating rate of 6 ° C / min. While applying a load of 1.96 MPa with a plunger and extruded from a nozzle with a diameter of 1 mm and a length of 1 mm. . Plot the plunger drop amount of the flow tester against the temperature, and let the softening point be the temperature at which half of the sample flows out.

[Glass transition point of resin]
Using a differential scanning calorimeter (Seiko Denshi Kogyo Co., Ltd., DSC210), the temperature was raised to 200 ° C, and the sample was cooled to 0 ° C at a temperature drop rate of 10 ° C / min. The temperature at the intersection of the extended line of the baseline below the maximum peak temperature of endotherm and the tangent line indicating the maximum slope from the peak rising portion to the peak apex.

[Acid value of the resin]
Measured according to the method of JIS K0070. However, only the measurement solvent was changed from the mixed solvent of ethanol and ether specified in JIS K0070 to the mixed solvent of acetone and toluene (acetone: toluene = 1: 1 (volume ratio)).

[Number average molecular weight of resin]
The number average molecular weight is obtained from a chart showing the molecular weight distribution by gel permeation chromatography obtained by the following method.
(1) Preparation of sample solution Dissolve the resin in tetrahydrofuran so that the concentration is 0.5 g / 100 mL. Next, this solution is filtered using a fluororesin filter having a pore size of 2 μm (FP-200, manufactured by Sumitomo Electric Industries, Ltd.) to remove insoluble components, thereby obtaining a sample solution.
(2) Molecular weight distribution measurement Using the following measuring device and analytical column, flow tetrahydrofuran at a flow rate of 1 mL per minute as a solution, and stabilize the column in a constant temperature bath at 40 ° C. Inject 100 μL of the sample solution into the sample and perform measurement. The molecular weight of the sample is calculated based on a calibration curve prepared in advance. For the calibration curve at this time, a sample prepared using several types of monodisperse polystyrene as a standard sample is used.
Measuring device: CO-8010 (manufactured by Tosoh Corporation)
Analytical column: GMHXL + G3000HXL (manufactured by Tosoh Corporation)

[Volume-median particle size of toner (D ₅₀ )]
In this specification, the volume-median particle size (D ₅₀ ) of the toner means the particle size of the toner in which the cumulative volume frequency calculated by the volume fraction is 50% calculated from the smaller particle size.
Measuring instrument: Coulter Multisizer II (Beckman Coulter, Inc.)
Aperture diameter: 50μm
Analysis software: Coulter Multisizer AccuComp version 1.19 (Beckman Coulter)
Electrolyte: Isoton II (Beckman Coulter)
Dispersion: Emulgen 109P (manufactured by Kao Corporation, polyoxyethylene lauryl ether, HLB: 13.6) 5% by weight Electrolyte dispersion condition: 10 mg of measurement sample was added to 5 mL of dispersion, and dispersed for 1 minute with an ultrasonic disperser. Thereafter, 25 mL of an electrolytic solution is added, and further dispersed with an ultrasonic disperser for 1 minute.
Measurement conditions: The dispersion is added to 100 mL of the electrolytic solution so that the particle size of 30,000 toner particles can be measured in 20 seconds, and 30,000 particles are measured. Determine the median particle size (D ₅₀ ).

Resin production example 1
Raw material monomers other than trimellitic anhydride shown in Table 1 and 11 g of tin (II) octylate (0.5 parts by weight with respect to 100 parts by weight of the total amount of alcohol component and carboxylic acid component) were introduced into a nitrogen introduction tube, dehydration tube, stirrer and It was placed in a 5-liter four-necked flask equipped with a thermocouple, reacted at 230 ° C. for 4 hours, and then reacted at 8.3 kPa for 1 hour. Furthermore, trimellitic anhydride shown in Table 1 was added at 215 ° C. and reacted until the desired softening point was reached to obtain resins H-1 to H-5.

Resin production example 2
Raw material monomers other than fumaric acid shown in Table 2 and 11 g of tin (II) octylate (0.5 parts by weight with respect to 100 parts by weight of the total amount of alcohol component and carboxylic acid component) were introduced into a nitrogen introduction tube, dehydration tube, stirrer and thermocouple. Was placed in a 5 liter four-necked flask equipped with a reactor, reacted at 230 ° C. for 8 hours, and then reacted at 8.3 kPa for 1 hour. Furthermore, at 190 ° C, 1 g of tertiary butyl catechol (0.05 parts by weight with respect to 100 parts by weight of the total amount of alcohol component and carboxylic acid component) and fumaric acid shown in Table 2 were added, and the reaction was continued until the desired softening point was reached. Resin L-1 to L-5.

Examples 1-7 and Comparative Examples 1-5
100 parts by weight of the binder resin shown in Table 3, 5.0 parts by weight of carbon black “Mogul L” (Cabot), 1.0 part by weight of negatively chargeable charge control agent “T-77” (Hodogaya Chemical), and 2.0 parts by weight of “Carnauba wax No. 1” (manufactured by Kato Yoko Co., Ltd.) was sufficiently mixed with a Henschel mixer.

  The obtained mixture was melt-kneaded by a co-rotating twin-screw extruder having a total kneading part length of 1560 mm, a screw diameter of 42 mm, and a barrel inner diameter of 43 mm. The barrel set temperature was 90 ° C. (kneaded material temperature: 120 to 140 ° C.), the screw rotation speed was 200 rotations / minute, the mixture supply speed was 10 kg / hour, and the average residence time was about 18 seconds.

The obtained kneaded material is rolled with a cooling roll and cooled to 20 ° C. or lower, and then coarsely pulverized by attaching a 3 mm mesh (mesh opening: 3 mm) screen to the rotoplex, and further, an I-2 type pulverizer Finely pulverized (classified by Nippon Pneumatic Co., Ltd.) and classified to obtain toner particles having a volume median particle size (D ₅₀ ) of 7.5 μm. The pulverization pressure when finely pulverized with an I-2 type pulverizer (manufactured by Nippon Pneumatic Co., Ltd.) was measured, and the pulverizability of the toner was evaluated according to the following evaluation criteria. The results are shown in Table 3.

〔Evaluation criteria〕
A: Grinding pressure is less than 0.30 B: Grinding pressure is 0.30 or more and less than 0.45 C: Grinding pressure is 0.45 or more

  To 100 parts by weight of the obtained toner particles, 0.65 parts by weight of hydrophobic silica “TS-530” (manufactured by Cabot) was added as an external additive, and mixed with a Henschel mixer to obtain a toner.

Test Example 1 [Low-temperature fixability, hot offset resistance]
Toner was mounted on a copier “AR-505” (manufactured by Sharp Corporation), and an unfixed image having a solid image portion of 2 cm × 12 cm (toner adhesion amount: 0.5 mg / cm ² ) was obtained. Using a fixing machine (fixing speed: 100 mm / sec) with an improved fixing machine for the copier “AR-505” (manufactured by Sharp Corporation) that can be fixed outside the machine, the fixing temperature is 90 ° C to 240 ° C. The unfixed image was fixed while gradually increasing to 10 ° C by 10 ° C.

  “Unicelohan tape” (Mitsubishi Pencil Co., Ltd., width: 18 mm, JIS Z-1522) was pasted on the fixed image, passed through a fixing roller set at 30 ° C., and then the tape was peeled off. Measure the optical reflection density before and after applying the tape using a reflection densitometer “RD-915” (manufactured by Macbeth), and the ratio of both (after peeling / before sticking) first exceeds 70%. The low temperature fixability was evaluated with the roller temperature as the minimum fixing temperature. The results are shown in Table 3.

At the same time, the occurrence of hot offset was visually observed, and the temperature at which hot offset occurred was confirmed as hot offset resistance. The paper used for the fixing test is “CopyBond SF-70NA” (manufactured by Sharp Corporation, 75 g / m ² ). The results are shown in Table 3.

Test Example 2 [Fixing roller peelability]
Toner was mounted on a copier “AR-505” (manufactured by Sharp Corporation), and an unfixed image having a solid image portion of 2 cm × 12 cm (toner adhesion amount: 0.5 mg / cm ² ) was obtained. Using a fixing machine (fixing speed: 100 mm / sec) that has been improved so that the fixing machine of the copier “AR-505” (manufactured by Sharp Corporation) can be fixed outside the machine, the fixing temperature is set to 170 ° C. The paper was passed through the fixing roller and visually observed whether it peeled off from the fixing roller or adhered to the fixing roller, and the fixing roller peelability was evaluated according to the following evaluation criteria. The results are shown in Table 3.

〔Evaluation criteria〕
A: Paper peels cleanly from the fixing roller.
B: Paper peels off from the fixing roller, but bends after passing.
C: Paper adheres to the fixing roller.

  From the above results, in Examples 1 to 7, compared with Comparative Examples 1 to 5, the toner has excellent pulverization properties, low-temperature fixability, hot offset resistance, and peelability from the fixing roller. I understand. On the other hand, for example, in Comparative Example 1, the low softening point polyester does not contain an ethylene oxide adduct of bisphenol A and has a large molecular weight difference between the polyesters. The sex is decreasing. In Comparative Example 2 in which the softening point difference of the polyester is too small, the hot offset resistance and the peelability from the fixing roller are lowered. In Comparative Example 3 in which the softening point difference of the polyester is too large, the grindability and low temperature fixing are further reduced. Sex is also getting worse. Moreover, since the difference between the softening points of the resins is 80 ° C. or more and the difference in molecular weight between the H-form and the L-form is too large, the resin is poorly dispersed and the hot offset resistance and the roller peelability are deteriorated.

  The toner for electrophotography of the present invention is suitably used for developing a latent image formed in electrophotography, electrostatic recording method, electrostatic printing method and the like.

Claims (7)

An electrophotographic toner comprising, as a binder resin, polyester H and polyester L having a softening point lower than that of polyester H by 55 to 80 ° C., wherein the polyester L contains 70 to 100 ethylene oxide adduct of bisphenol A. An electrophotographic toner, which is a polyester obtained by polycondensation of an alcohol component and a carboxylic acid component contained in mol%.   The toner for electrophotography according to claim 1, wherein the number average molecular weight of the polyester L is 1000-3500.   The toner for electrophotography according to claim 1 or 2, wherein the carboxylic acid component of at least one of polyester H and polyester L contains 50 mol% or more of an aromatic dicarboxylic acid compound.   The toner for electrophotography according to any one of claims 1 to 3, wherein the number average molecular weight of the polyester H is 2000 to 3400.   The toner for electrophotography according to any one of claims 1 to 4, wherein the acid value of polyester H is 1 to 10 mgKOH / g, and the acid value of polyester L is 5 to 20 mgKOH / g.   The toner for electrophotography according to any one of claims 1 to 5, wherein the softening point of polyester H is 135 to 160 ° C.   The toner for electrophotography according to any one of claims 1 to 6, wherein the softening point of the polyester L is 75 to 95 ° C.